You need to calibrate them. Give them placeholder values. Find the real and virtual distance between two positions. From there I adjust the placeholder steps/mm by multiplying by (virtual/real). I will try to remember to get the values I have when I get home. However, after we put in calibration data for each arm this will cease to be as important.

The number I came up with is 123.622 for X and Z and 121.260 steps/mm for Y. I have not seen Nicholas' number but apparently they are very similar. I can almost touch the bed at (133,133,133) while I see in his Segmentize positions list that he is very close at (133.2,133.2,133.1). So, while every machine could have a diferent number, this will put you in the ballpark.